Staple remover



Dec. 15, 1953 J. A. YERKES 2,662,727

STAPLE REMOVER Filed Feb. 17, 1949 3 Sheets-Sheet l .O was. 2. k9

INVENTOR. JOHN A .YERKES WFW A TTO/QNEYS Dec. 15, 1953 J. A. YERKES 2,662,727

' STAPLE REMOVER Filed Feb. 17, 1949 3 Sheets-Sheet 2 INVENTOR. JOHN A YERKEIS ATTORNEYS Dec. 15, 1953 J. A. YERKES 2,662,727

STAPLE REMOVER Filed Feb. 17, 1949 3 Sheets-Sheet 3 71 INVENTOR. JOHN A .YERKES Mm/(MAW ATTORNEYS Patented Dec. 15, 1953 UNITED STATES PATENT OFFICE 2,662,727 STAPLE REMOVER John A. Yerkes, New York, N. Y.

Application February 17, 1949, Serial No. 76,879

4 Claims. (Cl. 254-28) This invention relates to a staple pulling device for removing staples engaged in material such as papers, letters, laminated sheets, wood and the like, said staples being of the form placed in the material by conventional oflice staple machines.

Previously, it has been recognized that in removing staples clinched in tearable sheet materials, that a guard jaw must be inserted under the bridge of the staple and that it must remain in contact with the material while the staple is being pulled out. If such a guard, substantially as wide as the bridge of the staple, is not provided, the clinched legs often fail to unclinch and thus will tear vertically through the paper.

It also has been known that the act of forcing a bevelled jaw under the bridge of a staple frequently results in tearing of the paper because a tightly clinched staple resists the entry of the jaw and the staple is bodily thrust along the plane of the paper, thus tearing the paper. To avoid'this defect, it is common practice to provide opposed jaws which approach the staple from two sides, thereby neutralizing the thrust and permitting entry under the staple of the jaws without damage to the material.

With the use of a suitable guard jaw under the bridge of a staple adapted to remain in contact with the stapled material, it has been the practice in many cases to effect the removal of i the staple by employing cams, wedges, inclined planes, and the like, to force the staple legs to unclinch, as the opposed jaws are swung toward each other. In such cases, in effecting entry under the staple, one of theopposed jaws acts as a back-up member to neutralize the lateral thrust so that the staple is not carried bodily though the material along the plane of the paper, with consequent tearing. For this purpose, back-up shoulders, slotted plates, opposed cams, wide wedges, etc. have been used. Among the outstanding defects of such devices can be enumerated excessive friction causing greater operational effort and loss of sensitivity, as well as frequent failure to perform with very thin paper or with deeply embedded staples.

One of the objects of the invention is to provide a staple puller or remover which will be simple, economical to manufacture, convenient to operate, and which will remove staples without damaging the material engaged by the staple.

In one aspect of the invention, a lifting jaw and a guard jaw are employed. The lifting and guard jaws each are moved oppositely relative to each other into overlapping relationship under the bridge of the staple to be removed. Thereafter, continued swinging movement of the lifting jaw in the same direction will lift the staple so as to fully extract the same, the pivot ofthe lifting jaw being arranged so that the forces tending to move the staple laterally will be insufficient to tear even the thinnest paper.

By swinging the lifting jaw relatively toward the guard jaw, opposed jaws of the present device with bevelled or similar tips effect easy and safe entry under the bridge of a clinched staple. The guard jaw preferably is substantially as wide as the staple bridge and remains in contact with the stapled material. As soon as both jaws are safely under the bridge of the staple, the lifting jaw continues its swing increasingly higher and lifts the bridge of the staple gradually higher from the surface of the paper and entirely out of contact with the guard jaw, the lifting jaw performing the lifting operation by itself. The swing is continued until the staple is entirely extracted without excessive friction and without tearing even the thinnest onion-skin paper and with successful removal of the deeply embedded staples, the guard jaw merely serving to iron out the legs of the staple.

To achieve this result, the location of the pivot on which the lifting jaw swings is especially noteworthy. This pivot preferably is located so that:

A. The tips of the opposed jaws meet simultaneously at the bridge of a staple.

13. Both jaws safely enter under the bridge of the staple without substantially unclinching the legs.

C. The lifting jaw then lifts the staple bridge by itself and without assistance of the guard jaw gradually higher and higher from the surface of the paper and out of engagement with the guard jaw, minimizing friction.

D. The path of the lifting jaw is in an are so positioned that there will not be sufiicient thrust on the staple, in a direction along the plane of the paper, to tear the paper, notwithstanding the lack of the customary, frictionconducive, back-up means or equivalent, men-. tioned above.

Simplicity of construction is achieved by swinging the lifting jaw in a Single simple are relative to the guard jaw, avoiding the mechanical complications of a more complex movement. Means can be provided for preventing slippage of the staple out of engagement with the lifting jaw, as hereinafter described.

Another object of the invention is to provide a staple pulling device which may be easily operated by a pressure on the operating elements thereof continuously in one direction.

As mentioned, this is accomplished by locating the pivot of the swinging lifting jaw so that as the jaw carrier is moved inwardly, the jaws will enter under the bridge of the staple, further swinging movement of the lifting jaw carrier in the same direction serving to cause the lifting jaw to move in an arcuate path upwardly away from the guard jaw so as to raise the staple bridge away from the guard jaw. The initial wedging action of the jaws is only utilized for the purpose of moving the jaws under the staple bridge without unclinching the same.

In one form, there may be a body or carrier having the guard jaw means projecting inwardly or transversely thereof and along one edge. The pivot for the lifting jaw is located on an intermediate portion of said body above the guard jaw means and arranged so that the radius of the arc of movement thereof is relatively short. The body and swinging lifting jaw can be grasped in the hand, the body and guard jaw being placed on the material. Squeezing pressure of the hand will cause swinging movement of the lifting jaw to remove the staple, the lifting jaw swinging continuously in an arc as described.

These and other features, objects and advantages of the invention will become apparent from the following description and drawings which are merely exemplary,

In the drawings:

Figure 1 is an enlarged end view of the device.

Figure 2 is a vertical cross sectional view taken along the line 2-2 of Figure 1.

Figure 3 is a bottom view of the device of Figures l and 2.

Figure 4 is a top view of Figures 1 and 2.

Figure 5 is a side view, not enlarged, of the device shown in Figures 1 and 2.

Figure 6 is a fragmentary enlarged sectional view showing the jaws resting on the surface of the material engaged by the staple before said jaws have been operated so that they enter under the bridge of the staple to be removed.

Figure 7 is a sectional view taken along the lines l-l of Figures 6.

Figure 8 is a view similar to that shown in Figure 6 with the exception that the jaw ends have just started to pass into an overlapping relationship and to enter under the bridge of the staple.

Figure 9 is a view taken along line 99 of Figure 8.

Figure 10 is similar to Figures 6 and 8 with the exception that the jaws have been moved further relatitve to each other so that the jaws have completed their wedging action and the lifting jaw has arched the staple bridge upwardly and is in position to start to lift the staple from the material.

Figure 11 is a view taken in the direction of Figure 11-11 of Figure 10.

Figure 12 is similar to Figures 6 to 10 with the exception that the lifting jaw has moved further in its staple removing operation.

Figure 13 is a sectiton taken along the lines 13-43 of Figure 12.

Figure 14 is similar to Figures 6, 8, 10 and 12 with the exception that the staple has been completely withdrawn.

Figure 15 is a view taken along the line I5-l5 of Figure 14.

Figure 16 is a view similar to Figure 13 with the exception that a staple is shown wherein a one leg withdrawal operation is depicted.

Figure 17 is a side view of a modified form of the invention.

Figure 18 is an end view looking from the left of Figure 17, with the lifting jaw grasping wings omitted for clarity.

Figure 19 is an enlarged fragmentary sectional view of a modified form of jaw construction and wherein the lifting jaw carrier frame construction has been varied.

Figure 20 is a bottom view of Figure 19.

Figure 21 is an enlarged fragmentary view showing a lifting jaw similar to Figure 19 with the exception that the detent arrangement has a different form.

Figure 22 is a slightly different form of a lifting Jaw.

Figure 23 is a top view of Figure 22.

Figure 24 is a side view partially in section of another form of the invention.

Figure 25 is a plan view of a modified form of guard jaw for operating in conjunction the lifting jaw arrangement of this invention.

In the present invention, the lifting jaw and guard jaw are oppositely swung relatively together. Preferably, the pivot for the lifting jaw is located so that after the jaws have been inserted under the staple bridge without unclinching the staple, further swinging movement of the lifting jaw by itself will lift out the staple, the bottom of the guard jaw remaining in contact with the paper. The outside corners of the guard jaw iron out and straighten the legs of the staple being removed. The radius of arc of movement of the lifting jaw is made relatively short so that the upward or lifting component of force on the staple is sufficiently great compared to the lateral component, that there is no tendency to tear the paper. It will be understood that if the lateral thrust were sufficiently great, the legs of the staple would rip through the paper. The initial wedging movement of the jaws during the first part of the swinging is merely for the purpose of moving the jaws into overlapping relationship, there being no camming action relative to the staple or wedging action of the jaws relative to each other used in the extraction of the staple from the material.

The center of the arc described by the tip of the lifting jaw is arranged so that the travel upward of the tip higher and higher away from the paper will not take place until the tips of both jaws are safely under the bridge of the staple.

In a preferred embodiment, the axis of the pivot of the lifting jaw can be arranged so as to be substantially parallel to the material as the jaws move under the staple bridge, the radius being such that thereafter the tip of the lifting jaw will move higher and higher away from the material or in a rising arc. In said preferred form, the pivot is approximately located above the point where the jaws enter into overlapping relationship but it is to be understood that this relationship can be varied. The arc of the swinging movement of the lifting jaw is in a plane angularly disposed relative to the material; in the preferred form the said plane being substantially at right angles to the material, as distinguished from said are being in a plane parallel to the material.

In one form of the invention, frame or body 30 (Figs. 1 and 2) may be formed of sheet metal, said frame having laterally spaced guard jaws 3| formed integral therewith. The frame is U- shaped in transverse section as may be seen in Figures 3 and 4, there being a rear wall 36A formed at the base of the U. The lifting jaw ends or members 32 are formed on a swinging lifting jaw frame or means 33.,said frame being made of bent sheet metal if desired. The lifting portion or surface extending rearwardly from the tips is indicated generally at 32B. The lifting jaw swinging frame can be pivoted at 34 to a pin extending between the sidesof the guard jaw frame 30. A pair of stop pins 35 and 36 may be mounted in frame 30, there being a suitable spring 31 mounted on pivot pin34 cooperating with stop pin 35 and the portion 33A of frame 33 to hold the lifting jaw in a retracted position relative to the guard jaw 3 i It is to be understood that the various equivalent stop arrangements can be used such as inwardly projecting tongues struck in from the sides of the frame 30. Projections 33 of the swinging lifting jaw frame 33 can be arranged so that they limit outward movement by the spring 31, said projections limiting inward movement by contact withstop means 36, see dotdash line position 39. A slot 44 can be cut in each lifting jaw forming a staple detent 44A, said detent retaining the withdrawn staple and preventing one-leg withdrawal.

In Figure 7, a conventional staple 40 is depicted engaged in sheet material 4 I, said staple having a bridge portion 42 and a pair of clinched legs 43.

Guard jaws 3| and lifting jaws 32 are placed on the material with the staple 40 therebetween (Fig. 6). Upon initial pressure on the device so as to swing the lifting jaw frame inwardly, the tops of the jaws will start into an overlapping relationship as they enter underneath the bridge of the staple (Figs. 8, 9.). The bevel edge 3IA merely cooperates in a wedging action as the jaws move under.

Further movement of the jaws relative to each other to the position shown in Figures 10, 11 at which point, or before, the wedging-action stops, merely results in the raising of the bridge of the staple as the jaws slide thereunder without any substantial unclinching of the legs thereof.

Up to this point, tearing of the paper or other stapled material is avoided because the opposed jaws exert substantially equal and opposite thrust against the staple bridge holding the staple against lateral movement, which would tend to tear the paper.

After the lifting jaw is swung beyond the position shown in Figure 16, and approaches the position shown in Figures 12, 13 and beyond, the

staple bridge no longer is in contact with guard jaws 3| and the equalizing thrust mentioned above is no longer exerted by said guard jaws. To avoid tearing the paper as the movement of the lifting jaw continues, the location of the center of the pivot 34 is uniquely positioned so that the force exerted against the staple in a lateral direction (along the plane of the paper), will be inadequate to tear even the thinnest onion-skin paper. The unique arrangement of the parts as shown in the figures is of utmost importance.

As movement of the lifting jaws continues, the staple is lifted clear by the lifting jaws, the only function of the guard jaw being to iron out the legs of the staple. There is thus no camming action of the jaws in relation to each other during the actual lifting movement. As seen in Figure l2, the bridge of the staple has been moved clear of the guard jaw during the lifting movement.

Further swinging movement of the lifting jaw 6 frame will result in the complete withdrawalof the, staple from the material as indicated in Figures 14 and 15.

In the event there tends to be a so-called "one leg withdrawal in which one leg is unclinched while the other remains clinched, the detent arrangement will cause a binding on the staple at the bend of the 'unclinched leg and will grasp the staple so as to cause both legs to be withdrawn successively '(Fig. 16).

As can be seen in Figure 16, one leg 82 is still clinched, leg 83 having been drawn out until the bend thereof is engaged by the walls of the detent slot so as to prevent further movement. Further upward movement of the lifting jaw then will cause the other leg to be unclinched and withdrawn.

Long curved surfaces 45 may be provided at the bottom of the lifting jaw frame which tend to continuously, during the lifting action, assist in keeping the paper flat, thus eliminating the possibility of the tips of the guard jaw digging into the paper. Such curved surfaces, however, are not essential to the operation and may be omitted or shortened as in Figure 19.

A slightly different form of the remover is indicated in Figures 17 and 18 wherein the guard jaw frame 53 may have a lifting jaw frame 5i pivoted thereto at 52. The guard jaw frame has guard jaws 53 and lifting jaws 54, the lifting jaws being provided with a detent arrangement 55 similar to that previously described. The guard jaw frame 50 can have a plastic cover 56, said cover being fastened to the frame by means of fastening devices 57 and 58. The cover 56 has a pair of finger wings 53 extending therefrom to assist in holding the staple remover as it is operated. Lifting jaw frame 5| also may have a pair of finger wings 60 attached thereto by fastening means 6|. Theoperation of the form shown in Figures 17 and 18 is similar to that described previously for Figures 1 to 5. I

The jaws can be separately formed and fastened to the guardjaw frame and the lifting jaw frame. Referring to Figure 19, guard jaw frame 6| has a guard jaw 62 fastened thereto at 63 by a rivet, welding, or any other suitable means. The lifting jaw frame in this form is a reversed U with the transverse leg A at the inner or interior face thereof. The lifting jaw 64 is fastened to the lifting jaw frame 65 by means of the rivet 66 in the transverse leg 65A. In this form, the tip of the lifting jaw is formed as shown in Figure 20 and enters between the guard jaws 62. Detent 6'! is integral with the transverse leg 65A of the swinging lifting jaw frame 65.

The detent slot arrangement in the previously described forms is shown with straight parallel surfaces. It has been found that if the surfaces are arranged so that there is a double slope, that slippage of the staple out of the slot is made more unlikely. In Figure 21, lifting jaws 66 are formed on the lifting jaw frame 6TB, there being a transverse leg 61A. The retaining slot has a portion 63 of one slope and an inner portion 69 of a greater slope. The guard jaw is indicated at I0.

A further modification of the lifting jaw is illustrated in Figures 22 and 23 wherein the lifting jaws H are formed by bending downwardly the edges of flat sheet of metal. The detent 12 is in the form of a tongue projecting from the flat portion of the lifting jaw carrier frame.

It also is possible to pivot the lifting jaw frame on the guard jaw frame and to employ a pivoted operator therefor. In Figure 24, guard I jaw.

frame 12 is shown having a lifting jaw frame 13 pivoted thereto at 14, there being stop pins and 16 similar to those described for Figures 1 to 5, inclusive. An operating lever 11 is pivoted at T8 to said frame, said operating lever having a projection [9 bearing on the lifting jaw frame 12. A spring may be used for holding the lifting jaw frame in its inoperative position. When it is desired to operate the remover, the frame is grasped and operating arm 11 pressed inwardly. This will cause movement of the lifting jaw frame from the position shown at 13 to the dotted line position shown at 80, thus swinging the lifting jaws into overlapping relationship with the guard jaws so as to remove an engaged staple as described for the other forms of the invention.

The form described immediately above will be found convenient for some applications of the device as it combines the advantages of the uniquely positioned pivot 14 with the more conventionally pivoted lever 11, the latter requiring a generally smaller angular swing.

The guard jaws may have a pair of shoulders 8| (Fig. substantially as shown in the figure. In this form of the invention, the lifting jaw enters under the staple, swings as described above and the bridge of the staple is lifted out of contact with the guard jaw as in the other forms shown. However, in this form of the device, shoulders 8| abut the staple legs and assist in ironing them straight. This form has been found superior to similar devices in which the staple bridge is swept along and remains in contact with the guard jaw. The form shown in Figure 25, however, has been found to require more operating force than the preferred form shown in Figures 1 to 15, inclusive, but has the advantage of requiring less angular movement of the operating parts.

In the forms shown, the staple puller can be operated by placing the guard jaws on the material adjacent the bridge of the staple to be removed, the body or guard jaw frame being grasped by the hand or fingers, the hand or some of the fingers also grasping the lifting jaw swinging means which may be the outside or a portion of the lifting jaw frame or may be an element contacting the lifting jaws frame such as the swinging lever 11 (Fig. 24). Then by continuing squeezing pressure, the lifting and guard jaws will enter under the staple bridge and the lifting jaw by itself will lift the staple bridge upwardly and outwardly, the lifting jaw and bridge moving higher and higher away from the material to completely remove the staple from the material. During this operation, the guard jaw remains in contact with the material and irons out the legs of the staple, the detent means serving to assure complete removal.

The staple remover described herein is simple and will remove staples with ease as the lifting jaw means is swung inwardly relative to a guard jaw. Details of construction can be varied from those illustrated without departing from the spirit of the invention except as set forth in the appended claims.

I claim:

1. In a staple remover for extracting clinched staples from materials, the combination of a lifting jaw having a sharp tip adapted for entry under the bridge of a clinched staple and having an upper lifting surface adjoining said tip for engaging under and lifting said bridge; a guard jaw having a sharp tip for entry under said bridge and having an upwardy extending surface adjoining its tip, said surface comprising a backup surface for facilitating entry of said guard jaw tip under the bridge of said staple; said guard jaw having a lower ironing surface adjoining said tip; a pivot connecting both jaws and being fixed relative to both jaws around which said jaws may be swung; the tips of said jaws being substantially equidistant from said pivot when said jaws are in their inoperative position, as said lifting jaw is manually swung relatively toward said guard jaw, the tips of said jaws simultaneously enter under the bridge of said staple, said lifting surface and said backup surface entering under said staple bridge; said lifting surface being constrained by said pivot to swing in a predetermined arcuate path around said pivot; said guard jaw being positioned so that its tip intersects said arcuate path and with its upper surface so formed as to recede away from said path so that the bridge of said staple will be lifted by said lifting surface out of contact with said upper surface of said guard jaw before said staple legs are substantially unclinched; said ironing surface of said guard jaw remaining under the bridge of said staple and above the clinched legs of said staple during the entire act of extraction and pressing downwardly by reactive force against the stapled material and against said clinched legs to unbend said legs downwardly as said bridge is lifted upwardly by continued manual relative swinging of said lifting jaw until said staple is completely extracted.

2. In a staple remover for extracting clinched staples from materials, the combination of a lifting jaw having a sharp tip adapted for entry under the bridge of a clinched staple and having an upper lifting surface adjoining said tip for engaging under and lifting said bridge, said lifting jaw having detent means; a guard jaw having a sharp tip for entry under said bridge and having an upwardly extending surface adjoining its tip, said surface comprising a backup surface for facilitating entry of said guard jaw tip under the bridge of said staple; said guard jaw having a lower ironing surface adjoining said tip; a pivot connecting both jaws and being fixed relative to both jaws around which said jaws may be swung; the tips of said jaws being substantially equidistant from said pivot when said jaws are in their inoperative position, as said lifting jaw is manually swung relatively toward said guard jaw, the tips of said jaws simultaneously enter under the bridge of said staple, said lifting surface and said backup surface entering under said staple bridge; said lifting surface being constrained by said pivot to swing in a predetermined arcuate path around said pivot; said guard jaw being positioned so that its tip intersects said arcuate path and with its upper surface so formed as to recede away from said path so that the bridge of said staple will be lifted by said lifting surface out of contact with said upper surface of said guard jaw before said staple legs are substantially unclinched; said ironing surface of said guard jaw remaining under the bridge of said staple and above the clinched legs of said staple during the entire act of extraction and pressing downwardly by reactive force against the stapled material and against said clinched legs to unbend said legs downwardly as said bridge is lifted upwardly by continued manual relative swinging of said lifting jaw until said staple is completely extracted.

3. In a staple removed for extracting clinched staples from materials, the combination of a lifting jaw having a sharp tip adapted for entry under the bridge of a clinched staple and having an upper lifting surface adjoining said tip for engaging under and lifting said bridge, said liftsurface ling an overlying member for providing a detent space betweensaid lifting surface said overlying member, said space being insubstantially higher than the thickness of the staple wire and being at least long as the width of the staple wire; a guard having a sharp tip for entry under said bridge and having an upwardly extending surface adjoing its tip, said surface comprising a backup surface for facilitating entry of said guard jaw tip under the bridge of said staple; said guard jaw having a lower ironing surface adjoining said tip, a pivot connecting both jaws and being fixed relative to both jaws around which said jaws may be swung; the tips of said jaws being substantially equidistant from said pivot when said jaws are in their inoperative positicn, as said lifting jaw is manually swung relatively toward said guard jaw, the tips of sair jaws simultaneously enter under the bridge of said staple, said lifting surface and said backup surface entering under said staple bridge; said lifting surface being constrained by said pivot to swing in a predetermined arcuate path around said pivot under the bridge of said staple and upwardly away from the stapled materials; said guard jaw being positioned so that its tip intersects said arcuate path and with its upper surface so formed as to recede away from said path so that the bridge of said staple will be lifted by said lifting surface out of contact with said upper surface of said guard jaw before said staple legs are substantially unclinched; said ironing surface of said guard jaw remaining under the bridge of said staple and above the clinched legs of said staple duringthe entire act of extraction and pressing downwardly by re" active force against the stapled material and against said clinched legs to unbend said legs downwardly as said bridge is lifted upwardly by continued manual swinging of said lifting jaw relative to said guard jaw until said staple is completely extracted.

4. In a staple remover for extracting clinched staples from materials, the combination of a lifting jaw having a sharp tip adapted for entry under the bridge of a clinched staple and having an upper lifting surface adjoining said tip for engaging under and lifting said bridge, said lifting surface having an overlying member for providing a detent space between said lifting surface and said overlying member, said space being insubstantially higher than the thickness of the staple wire and being at least as long as the width of the staple wire; a guard jaw having a sharp tip for entry under said bridge and having an upwardly extending surface adjoining its tip, said surface comprising a backup surface for facilitating entry of said guard jaw tip under the bridge of said staple; said guard jaw having a lower ironing surface adjoining said tip; said guard jaw having outer side walls, the side walls substantially being spaced apart a distance less than the distance between the bent legs of said staple at all points on said guard jaw reached by said legs during extraction; a pivot connecting both jaws and being fixed relative to both jaws around which said jaws may be swung; the tips of said jaws being substan tially equidistant from said pivot when said jaws are in their inoperative position, as said lifting jaw is manually swung relatively toward said guard jaw, the tips of said jaws simultaneously enter under the bridge of said staple, said lifting surface and said backup surface entering under said staple bridge; said lifting surface being constrained by said pivot to swing in a predetermined arcuate path around said pivot under the bridge of said staple and upwardly away from the stapled materials; said guard jaw being positioned so that its tipintersects said arcuate path and with its upper surface so formed as to recede away from said path so that the bridge of said staple will be lifted by said lifting surface'out of contact with said upper surface of said guard jaw before said. staple legs are substantially unclinched; said ironing surface of said guard jaw remaining under the bridge of said staple and above the clinched legs of said staple during the entire act of extraction and pressing downwardly by reactive force against the stapled material and against said clinched legs to unbend said legs downwardly as said bridge is lifted. upwardly by continued manual swinging of said lifting jaw -elative to said guard jaw until said staple is completely extracted.

JOHN A. YERKES.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,033,050 Pankonin i- Mar. 28, 1936 2,192,087 Pankonln Dec. 14, 1937 2,431,922 Curtiss Dec. 2, 19 2,4;99/i32 Von Cseh Mar. 7, 1950 2,539,171 Yerkes Jan. 23, 1951 2,549,250 Sudbury Apr. 17, 1951 2,553,660 Levendesky May 22, 1951 

